Methods and apparatus for high voltage integrated circuit capacitors

ABSTRACT

High voltage integrated circuit capacitors are disclosed. In an example arrangement. A capacitor structure includes a semiconductor substrate; a bottom plate having a conductive layer overlying the semiconductor substrate; a capacitor dielectric layer deposited overlying at least a portion of the bottom plate and having a first thickness greater than about 6 um in a first region; a sloped transition region in the capacitor dielectric at an edge of the first region, the sloped transition region having an upper surface with a slope of greater than 5 degrees from a horizontal plane and extending from the first region to a second region of the capacitor dielectric layer having a second thickness lower than the first thickness; and a top plate conductor formed overlying at least a portion of the capacitor dielectric layer in the first region. Methods and additional apparatus arrangements are disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. Nonprovisional patentapplication Ser. No. 14/933,638, filed Nov. 5, 2015, which claims thebenefit of U.S. Provisional Application Ser. No. 62/076,176, filed Nov.6, 2014, the contents of both of which are herein incorporated byreference in its entirety.

TECHNICAL FIELD

The present application relates in general to electronic circuitry andin particular to methods and apparatus for building integrated highvoltage and extra-high voltage capacitors within a semiconductormanufacturing process.

BACKGROUND

In modern industrial equipment, computer controllers are being utilizedin greater numbers of applications. The need for electrical isolationbetween the low voltage of controllers and the high voltage of motors orequipment is growing. Depending on the equipment being controlled, thereare various known approaches used to isolate the systems electricallybut that still allow electrical coupling. Isolation provides an AC pathfor signals or power between two circuits but eliminates directconnections. This is important where ground potential differences existbetween nodes. Isolation is used to break the direct connection pathsbetween the signal domains and to break the common ground loop, becausenoise can be transmitted through the ground loop that would otherwiseinterfere with the proper operation of the circuits. Known isolationapproaches can include using a transformer to couple circuitsmagnetically, an RF signal to couple through a radiated energy, anopto-isolator using light energy, or using a capacitor between the twocircuits that couples the circuits using an electric field. Otherisolation needs include integration of analog and digital circuitry ontoa single packaged integrated circuit with separate power domains, forexample.

Although opto-isolators are a suitable solution for low speedcommunication applications, in other applications where isolation isrequired and an opto-isolator is not appropriate, a capacitor is needed.Capacitors provided on a circuit board or as part of the package forintegrated circuits have been used for isolation, for example, U.S. Pat.No. 4,780,795, entitled “Packages for Hybrid Integrated Circuit HighVoltage Isolation Amplifiers and Method of Manufacture,” issued Oct. 25,1988 to Meinel, discloses a hybrid package for integrated circuits thatincludes two silicon integrated circuit devices positioned within apackage and the use of planar discrete capacitors formed on a ceramicsubstrate also within the package for isolation between the two siliconcircuits. However as integration of circuits onto silicon continues toadvance, isolators that can be formed on the semiconductor substratewith other circuitry, e.g., integrated capacitor isolators, are used anddesired. To gain increased capacitance values for use with highervoltages, the capacitors used in the prior known approaches can becoupled serially, however, this approach requires additional siliconarea. Integrated capacitors of values capable for high voltage isolationare therefore desired. These capacitors could be used serially to gainstill higher capacitor values, or the isolation capacitors could be usedto form discrete components as well as being used in integrated circuitswith additional circuitry.

Within the present application and as currently described in the powercircuits industry, low voltage is considered as below 50V, high voltageis defined as a voltage greater than 50 Volts and less than 5,000 volts.Extra-high voltage is a voltage greater than 5,000 Volts and less thanabout 20,000 Volts. Arrangements herein are directed at high voltage andextra-high voltage applications.

With the trend for miniaturization, control interfaces utilizingintegrated capacitors for isolation are needed. Integrated capacitorsprovide the smallest solution for isolation and power circuitapplications. However, in the prior known approach solutions, to createan integrated capacitor in the extra-high voltage range, greater than5,000 Volts peak for example, the large capacitance needed has beenformed by coupling two or more lower voltage capacitors in series.Increased capacitor values are therefore desired to further reduce thesilicon area needed to achieve a particular isolation circuit solution.

The breakdown voltage of an ideal parallel plate capacitor is related tothe dielectric strength and distance between the plates as shown inEquation 1:

V_(bd)=E_(ds)d   EQUATION 1

Where:

V_(bd)=breakdown voltage; E_(ds)=dielectric strength and d=distancebetween plates

Equation 1 illustrates that for a constant dielectric material,increasing the distance between the capacitor plates will linearlyincrease the breakdown voltage. In an integrated circuit, where twodifferent metal layers may typically form the capacitor plates, theplate distance d is increased by increasing the dielectric thicknessbetween the layers. However, in an integrated circuit process, adielectric thickness increased to a distance sufficient for high voltagecapacitors can also lead to wafer bowing or warpage, and to increase thedielectric thickness enough so that the V_(br) is greater than 5,000volts, the wafer warpage can become so pronounced that semiconductorprocessing equipment downstream from the dielectric thickening step isnot able to properly process the wafers. In addition, in a knownapproach that uses the typical multiple level metal layer systems withinter-metal dielectrics to achieve a sufficiently thick dielectric forhigh voltage capacitors, the process of adding multiple layers of metaland oxide, then stripping away the unwanted metal areas so as to createthe desired dielectric thickness results in electrical degradation ofthe capacitor. The additional process operations of forming metal,photoresist, etch, leveling/planarization such as chemical mechanicalpolishing (CMP) and clean-up cause increased defects and add extra coststo the production of the wafer, which are undesirable. However, in anintegrated circuit process, increasing the dielectric thickness to adistance sufficient for high voltage and extra-high voltage capacitorshas a number of challenges. Extremely thick layers of generallycompressive dielectric films can lead to severe wafer warpage, such thatsemiconductor processing equipment downstream from the dielectricdeposition step is not able to properly process the wafers. In addition,embedding additional metal levels for no reason other than to increasethe dielectric thickness between bottom and top plates of the capacitorresults in a significant cost increase related to the repeatedprocessing loop of forming inter-level connection vias, then a patternedmetal layer, then depositing and planarizing a dielectric material overthe metal layer.

Continuing improvements are therefore needed for methods and apparatusto provide integrated high voltage and extra-high voltage valuecapacitors that can be manufactured using conventional semiconductorprocessing methods and with known equipment, and at a relatively lowcost.

SUMMARY

An aspect of the present application provides methods and structures fora high voltage and extra-high voltage integrated circuit capacitor toaddress the deficiencies describe in existing art. In the arrangements,a thick capacitor dielectric structure is formed overlying a bottomplate and arranged to provide high voltage or extra high voltageintegrated capacitor arrangements.

In an example arrangement, a capacitor structure includes asemiconductor substrate; a bottom plate including a conductive layeroverlying the semiconductor substrate; a capacitor dielectric layerdeposited overlying at least a portion of the bottom plate and having afirst thickness greater than about 6 um in a first region; a slopedtransition region in the capacitor dielectric at an edge of the firstregion, the sloped transition region having an upper surface with aslope of greater than 5 degrees from a horizontal plane and extendingfrom the first region to a second region of the capacitor dielectriclayer having a second thickness lower than the first thickness; and atop plate conductor formed overlying at least a portion of the capacitordielectric layer in the first region.

In a further arrangement, the capacitor structure above wherein thecapacitor dielectric layer is an oxide, and further including at leastone layer of dielectric material formed between the capacitor dielectriclayer and the bottom plate that further comprises at least one ofsilicon nitride and silicon oxynitride.

In still another arrangement, the capacitor structure above is providedwherein the capacitor dielectric layer is a monolithic layer formed in asingle deposition step. In an additional arrangement, the capacitorstructure described above is provided wherein the capacitor dielectriclayer comprises an oxide formed by a TEOS deposition process. In afurther alternative arrangement, in the capacitor structures above, thecapacitor dielectric layer comprises multiple dielectric layers formedusing multiple deposition steps.

In still another arrangement, in the capacitor structures describedabove, wherein the multiple dielectric layers are formed using multipleTEOS deposition steps.

In yet another alternative arrangement, in the capacitor structuresdescribed above, the capacitor dielectric layer includes multipledielectrics formed as alternating compressive stress and tensile stresslayers. In still a further alternative arrangement, in the capacitorstructures described above, at least two of the multiple dielectriclayers are formed using multiple TEOS deposition steps of silicondioxide. In yet another arrangement, in the capacitor structuresdescribed above, a sum of the thicknesses of the capacitor dielectriclayer and the at least one layer of dielectric is greater than about 8ums. In still a further arrangement, in the capacitor structuresdescribed above, the capacitor dielectric layer has a thickness betweenabout 6 ums and about 15 ums.

In still another alternative arrangement, in the capacitor structuresdescribed above, the capacitor dielectric layer further comprises anupper layer comprising silicon nitride and silicon oxynitride formedbetween the capacitor dielectric layer and the top plate conductor. Inyet a further arrangement, in the capacitor structure described abovethe upper layer of the capacitor dielectric layer further comprisesopenings made in the upper layer.

In still a further arrangement, in the capacitor structures describedabove, the capacitor dielectric layer further comprises an area that isless than 35% of a total surface area of the semiconductor substrate. Inan another alternative arrangement, in the capacitor structuresdescribed above, the capacitor dielectric layer further comprises anarea that is between about 25% and about 35% of a total surface area ofthe semiconductor substrate.

In an example method arrangement, a method includes providing asemiconductor substrate; forming a capacitor bottom plate of conductivematerial overlying the semiconductor substrate; forming a capacitordielectric layer overlying at least a portion of the capacitor bottomplate, the capacitor dielectric layer having a thickness of at least 6ums; forming a gradient photoresist layer over the capacitor dielectriclayer defining a first region in the capacitor dielectric having a firstthickness and a defining a second region having a second thickness thatis less than the first thickness; etching the capacitor dielectric layerto form the first region, the second region, and forming a transitionregion between the first region and the second region, the transitionregion having a sloped top surface with a slope from a horizontal planegreater than about 5 degrees; and forming a top plate conductoroverlying at least a portion of the first region of the capacitordielectric layer.

In still another arrangement, the method above is performed and furtherforming the capacitor dielectric layer includes forming in a singledeposition step a monolithic capacitor dielectric layer that is oneselected from the group consisting essentially of an oxide layer and anoxynitride layer.

In still another alternative arrangement, the methods above areperformed and further include wherein forming in a single depositionstep further includes performing a TEOS deposition. In a furtheralternative arrangement, in the methods above, forming the capacitordielectric layer further includes forming the capacitor dielectric layerin a series of dielectric deposition steps to form multiple layers ofdielectric. In still another arrangement, in the methods above, formingthe multiple layers of dielectric comprises forming a series of layerseach one selected from the group consisting essentially of an oxidelayer and an oxynitride layer.

In yet another arrangement, in performing the methods described above,forming the capacitor dielectric layer further includes performing aseries of dielectric deposition steps to form alternating compressivelayers and tensile layers of dielectric.

In an additional alternative method, the methods above are performed andfurther include forming at least one insulating layer between the bottomplate and the capacitor dielectric layer, the insulating layer having athickness of at least 1.5 ms.

In still another additional alternative arrangement, the methodsdescribed above are performed and include wherein a sum of thethicknesses of the capacitor dielectric layer and the thickness of theat least one insulating layer is greater than about 9 ms.

In a further method arrangement, the methods described above areperformed and an area of the capacitor dielectric layer is less than 35%of a total area of the semiconductor substrate. In still anotherarrangement, the methods described above are performed and furthercomprising forming an upper layer over the capacitor dielectric layerthat lies between the top of the capacitor dielectric layer and the topplate conductor, the upper layer comprising silicon nitride and siliconoxynitride. In still another alternative arrangement, the above methodsare performed and further including forming openings in the upper layerby photolithographic pattern and etch processes.

In another example arrangement, an integrated circuit includes: asemiconductor substrate; at least one integrated isolation capacitor onthe semiconductor substrate, the at least one integrated capacitorfurther including a bottom plate comprising a conductive layer overlyingthe semiconductor substrate; a capacitor dielectric layer depositedoverlying at least a portion of the bottom plate and having a firstthickness greater than about 6 ums in a first region, and having asecond thickness less than the first thickness in a second region, andhaving a sloped transition region extending from the first region to thesecond region with an upper surface sloped at least 5 degrees from ahorizontal plane; and a top plate conductor formed overlying at least aportion of the capacitor dielectric layer in the first region; at leastone circuit coupled to the bottom plate of the at least one integratedcapacitor; and an integrated circuit terminal coupled to the top plateof the at least one integrated capacitor and galvanically isolated fromthe at least one circuit by the integrated capacitor.

In still a further arrangement, the above described integrated circuitis provided wherein the at least one integrated capacitor furtherincludes at least one layer of dielectric material disposed between thebottom plate and the bottom of the capacitor dielectric layer.

Use of the novel arrangements of the present application enable a singleintegrated circuit capacitor with dielectric thicknesses that allow forthe breakdown voltages needed for high voltage and extra-high voltagecapacitors and applications.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the illustrative examples ofaspects of the present application that are described herein and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 is graph illustrating the effectiveness of a novel MESA processof the arrangements in creating high voltage and extra-high voltagecapacitors;

FIG. 2 depicts in a cross-sectional view a portion of a high voltage oran extra-high voltage capacitor arrangement utilizing the novel MESAstructure formation after initial processing;

FIG. 3 depicts in another cross-sectional view a portion of a highvoltage or an extra-high voltage capacitor utilizing the MESA formationarrangement as in FIG. 2 at a subsequent processing step;

FIG. 4 depicts in another cross-sectional view a portion of a highvoltage or an extra-high voltage capacitor utilizing the MESA formationarrangement as in FIG. 3 at a subsequent processing step, ready for theMESA etch;

FIG. 5 depicts in another cross-sectional view a portion of a highvoltage or an extra-high voltage capacitor utilizing the MESA formationarrangement as in FIG. 4 at a subsequent processing step, after an etchstep;

FIG. 6 depicts in a further cross-sectional view a portion of a highvoltage or an extra-high voltage capacitor utilizing the MESA formationarrangement as in FIG. 5 at a subsequent processing step, illustratingthe formation of the top capacitor plate;

FIG. 7 depicts in a further cross-sectional view a portion of a highvoltage or an extra-high voltage capacitor utilizing the MESA formationarrangement as in FIG. 6 after depositing a passivation overcoatoxide/SiON bilayer;

FIG. 8 depicts in a further cross-sectional view a portion of a highvoltage or an extra-high voltage capacitor utilizing the MESA formationarrangement as in FIG. 7 after preferentially removing the passivationovercoat from the regions where wire bonds (or other bonding method)will be formed;

FIG. 9 depicts in another cross-sectional view of a high voltage or anextra-high voltage capacitor utilizing the MESA formation arrangement asin FIG. 8 at a subsequent processing step, ready for polyimide pattern;

FIG. 10 depicts in another cross-sectional view a completed high voltageor extra-high voltage capacitor utilizing the novel MESA formation ofthe arrangements;

FIG. 11 depicts in a cross sectional view a portion of a high voltagecapacitor dielectric using the MESA structure of the arrangements,illustrating a single oxide deposition;

FIG. 12 depicts in another cross sectional view a portion of a highvoltage capacitor dielectric using the MESA structure of thearrangements, illustrating a multiple step oxide deposition;

FIG. 13 depicts in a further cross sectional view a portion of a highvoltage capacitor dielectric using an alternative MESA structure of thearrangements, illustrating a multiple step oxide deposition with tensileand compressive stress layers;

FIG. 14 depicts in yet another cross sectional view a completed highvoltage or extra-high voltage capacitor incorporating a novel MESAstructure of the arrangements;

FIG. 15 depicts in another cross sectional view a completed high voltageor extra-high voltage capacitor incorporating a novel MESA structure ofthe arrangements;

FIG. 16 depicts in a top view a portion of a high voltage or extra highvoltage capacitor formed using the novel MESA structure of thearrangements;

FIG. 17 is a flow chart of the method arrangement for creating a MESAcapacitor structure;

FIG. 18 depicts in a block diagram an example application for isolationusing a capacitor of the arrangements in a circuit arrangement;

FIG. 19 depicts in a circuit diagram an application for isolationcapacitors; and

FIG. 20 depicts in a block diagram an example arrangement incorporatingthe isolation capacitors of the present application.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the illustrativeexample arrangements and are not necessarily drawn to scale.

DETAILED DESCRIPTION

The making and using of various example illustrative arrangements thatincorporate aspects of the present application are discussed in detailbelow. It should be appreciated, however, that the illustrative examplesdisclosed provide many applicable inventive concepts that can beembodied in a wide variety of specific contexts. The specific examplesand arrangements discussed are merely illustrative of specific ways tomake and use the various arrangements, and the examples described do notlimit the scope of the specification, nor do they limit the scope of theappended claims.

For example, when the term “coupled” is used herein to describe therelationships between elements, the term as used in the specificationand the appended claims is to be interpreted broadly, and while the term“coupled” includes “connected”, the term “coupled” is not to be limitedto “connected” or “directly connected” but instead the term “coupled”may include connections made with intervening elements, and additionalelements and various connections may be used between any elements thatare described as “coupled.”

An aspect of the present application provides for methods and apparatusto fabricate a high voltage or extra-high voltage integrated capacitoron a wafer within a semiconductor fabrication process flow. Thefabrication technique utilizes a thick dielectric layer, called a “MESA”formation, formed in the upper portions of a semiconductor wafer, andthe thick capacitor dielectric is used to increase the distance betweenthe capacitor plates on the wafer. Because the thick dielectric layer isvertically above the remainder of the surface of the substrate and has aflat upper surface, it appears as a mesa shape. In the fabrication ofthe MESA capacitor, only standard semiconductor processes used incurrent production are utilized and an advantageous aspect of thepresent application is the ability to integrate the high voltagecapacitor within standard wafer production processes. Throughout thedetailed description, well known processes or operations are identifiedbut not shown in full detail to prevent from obscuring the aspects ofthe present application. One skilled in the relevant art will recognizethat aspects of the present application can be fabricated without one ormore of the specific details or by using another known method in afabrication step. The inventors of the present application contemplatealternative arrangements that can be formed in addition to the examplearrangements described for illustration purposes herein, and thesealternatives form additional novel arrangements that are contemplated asproviding additional aspects of the present application, and thesealternative arrangements fall within the scope of the appended claims.The additional capability of the MESA dielectric structures of thearrangements to increase the breakdown voltage of the capacitors is akey feature of the arrangements and is illustrated in FIG. 1.

FIG. 1 is a graph 100 illustrating the effectiveness of the MESA processin creating high voltage and extra-high voltage capacitors. In FIG. 1,the vertical axis plots the breakdown voltage (V_(br)) in Volts RMS, thehorizontal axis plots the capacitor dielectric thickness in um, where 1um=10,000 A (Angstroms). In graph 100, three data sets are illustrated:line 110 represents the V_(br) of an available integrated high voltagecapacitor; line 120 represents the current known art in high voltageintegrated circuit capacitors and extra-high voltage integratedcapacitors as designed using prior approaches, and dotted line 122indicates an extension of line 120 that is enabled due to the use of thenovel MESA structures and arrangements of the present application.

Data line 110 illustrates a dielectric that is the product of buildingmultiple layers of dielectric/metal layers (using a typical multiplelevel metal process) but with the intervening metal layers removed so asto form a dielectric stack. The etching of metal away between thedielectric layers (the metal being part of the conventional multiplelevel metal structure for integrated circuits formed in thesemiconductor process) has a cumulative degradation to the breakdownvoltage V_(br). The degradation is indicated by the data line 110 notbeing linear, but instead moving closer to the horizontal axis as thedielectric thickness increases. Line 120 illustrates the breakdownvoltage V_(br) for the high and extra-high voltage integrated circuitcapacitors formed using known approaches to forming a single layerdielectric, and the dotted line 122 represents the improvement in V_(br)due achieved due to the increased thickness that is enabled by the useof the novel MESA structures of the present application, described infurther detail below. The graph in FIG. 1 thus illustrates that by usingthe arrangements of the present application, increased breakdownvoltages for a single integrated capacitor which were previouslyunattainable can now be attained.

Throughout this application, many acronyms familiar to the semiconductorindustry are used. Some of those are IC (integrated circuit), CMP(Chemical Mechanical Polish), CVD (chemical vapor deposition), PECVD(Plasma Enhanced CVD), HDP (high density plasma), PO (ProtectiveOvercoat) and TEOS (silicon oxide formed from a tetraethylorthosilicatesource).

FIG. 2 depicts in a cross-sectional view a first step in a series ofexample process steps described herein for illustrating a non-limiting,example approach to forming a high voltage or extra-high voltagecapacitor utilizing the MESA structure and methods of the presentapplication. FIG. 2 illustrates in a cross section 200 a structure shownat the beginning of the formation of the bottom capacitor plate. Forcontinuity, the base numbers of the layers will be preserved insubsequent figures. Depicted in FIG. 2 is a semiconductor substrate 210,the processing layers 212 that have been deposited in prior conventionalsemiconductor processing steps, and the metal layer 220 which willbecome a bottom capacitor plate in the final capacitor arrangement. Inthe layer 212, the prior processing steps may form various devices (notshown for simplicity) in the substrate and interconnect them, such astransistors including MOS transistors, bipolar transistors, FETs,diodes, resistors, inductors, capacitors and the like. These componentscan be interconnected using metal layers and inter-metal dielectriclayers, the metal layers being connected to one another and to thesubstrate using via and contacts to connect the layers as are known tothose skilled in the art.

The versatility of the MESA structure of the arrangements of the presentapplication allows the capacitor structure to be built on differentsemiconductor fabrication processes containing as few as two levels ofmetal and as many as eight or more levels of metal. The initial orbottom capacitor plate can be formed within any of the metal levelsfabricated during the semiconductor processing of the layers 212 or 220.In the non-limiting example illustrated here, the MESA structure will befabricated utilizing the top level metal 220 as the bottom capacitorplate. Metal layer 220 can be, for example, aluminum or copper or alloysthereof, the metal being the one used in the particular semiconductorfabrication process. Single and dual damascene copper or copper alloymaterials can be used to form metal layer 220.

FIG. 3 depicts in another cross sectional view 300 a high voltage or anextra-high voltage capacitor utilizing the MESA formation at asubsequent step, at a stage ready for the MESA dielectric layers. Forcontinuity, the base numbers have been preserved from the previousfigure only incrementing the left digit to “3” including the substrate310, the prior processing layers 312 and the top level metal bottomcapacitor plate 320.

At this stage of processing in FIG. 3, on the top metal plate 320 anoptional migration barrier 322 can be applied at a thickness in therange of 800 A to 1100 A. In one example arrangement the layer 322 canbe silicon nitride formed using known deposition processes such as CVDor by a HDP process. Alternatives include SiCN layers and otherdielectrics used as barrier layers. The next layer shown in the crosssection 300 is a silicon dioxide layer 324. This may be referred to asthe “sub-ESL” layer, as it lies beneath an etch stop layer or ESL. In anexample arrangement this layer can be approximately 2500 A to 4500 Athick and can be applied by known oxide deposition processes. In thenon-limiting illustrative example depicted in FIG. 3, etch stop layer326 follows and can be formed approximately 2500 to 4500 A thick byknown processes. Etch stop layers are chosen so that selective etchchemistry of the overlying layer (to be described next) can be used.Etch stop layer 326 can be formed of SiON, for example, or oxynitride,or another dielectric that differs from the MESA dielectric layer to beformed next, so that a selective etch of silicon dioxide MESA material(described below) can be performed.

At this point in the fabrication the thick primary MESA TEOS layer 330is applied to the wafer using known processes such as CVD or PECVD. Inthis non-limiting example arrangement, a simple and cost effectivemethod is to deposit a single thick layer of TEOS silicon oxide. Thethickness of the primary MESA TEOS layer 330 can be determined by theevaluating the desired breakdown voltage Vbr required and the thicknessof layer 330 can be limited by the amount of temporary wafer bow orwafer warpage that can be tolerated in the semiconductor fabricationprocess. For tuning the breakdown voltage, the primary MESA TEOS layer330 may be applied in a range of approximately 6 um to 20 um (60,000 Ato 200,000 A) thick with thicker layers providing the highest breakdownvoltage and also carrying the highest risk for wafer warpage. Howeverforming a single deposition layer of the required thickness in a singleprocessing step, while practical, can impose difficulties on theprocessing equipment. For example, if a single TEOS deposition of morethan 8 ums is performed in one deposition step, a layer of silicon oxideof the same thickness deposits on the walls of the processing chamber.This wall oxide has to be removed from the process chamber using aplasma etch and clean process, which can be quite lengthy when the walloxide is of this thickness, affecting tool downtime and throughput ratein the semiconductor processing facility or tool. The inventors of thepresent application contemplate that the primary MESA TEOS layer 330 canbe, in some alternative arrangements of the present application, appliedin thinner layers in a sequence of deposition steps. In anotheralternative arrangement that is also described below, the layers can beapplied in successive layers of compressed and tensile stressor oxidelayers formed in multiple deposition steps to help mitigate the amountof wafer warpage. Further, the inventors contemplate additionalarrangements wherein the TEOS layer 330 can be formed using a process ofsuccessive, thinner oxide deposition steps with cooling steps betweenthe oxide depositions, improving wafer bow effects and reducing stresson the wafer. These alternative arrangements are also further describedin detail below.

The thickness of the total dielectric required for a particularcapacitance value influences the amount of wafer bow or warpage thatwill occur and impacts the decision about whether to use single ormultiple dielectric layers in creating the primary MESA TEOS layer 330.

FIG. 4 depicts in another cross sectional view 400 a portion of a highvoltage or extra-high voltage capacitor utilizing the MESA formation, ata subsequent processing stage now ready for photoresist exposure toprepare the MESA etch. For continuity, the base numbers of the layershave been preserved from the previous figures only incrementing the leftdigit to “4” including the substrate 410, the prior processing layers412, the bottom capacitor plate 420, the metal diffusion barrier 422,the initial MESA oxide layer 424, the etch stop layer 426 and theprimary MESA TEOS layer 430. A photoresist layer 431 is shown depositedover the MESA layer 430.

At the stage of the processing in FIG. 4 the thick primary MESA layer430 may be causing some wafer warpage because of its thickness. Sincethe eventual MESA area only requires about 15% to 35% of the total waferarea, etching away the unneeded MESA TEOS material 430 will relieve thestress on the wafer, reducing the wafer warpage which will allowsubsequent semiconductor processing to proceed without issues from thewarpage. However, an etch that leaves a stepped or steep edge at theMESA boundary could also cause subsequent processing steps to leavemetal fragments near the MESA edge, which will facilitate prematurevoltage breakdown. To alleviate this issue, a sloped edge on the MESA isformed in the area labeled 445. To enable this sloped area, a photomask460 is utilized where the area above the MESA (462) is fully chromed andthe area where no MESA material is desired is fully clear (466). Thetransition between the areas 462 and 466 on the photomask is a ditheredarea (464) where the side closest to 462 would have full chrome and thearea closest to 466 would have no chrome in the pattern. When used todevelop photoresist 431 and then a subsequent oxide etch is performedusing the resulting resist pattern, this essentially causes an etch“gradient” across the area 445 which leaves a sloped edge on the thickMESA oxide area after etch. Utilizing a mask of this description, thephotoresist 431 is exposed and patterned, and then the MESA material 430is etched with known photoresist and etch processes leaving a slope inarea 445. In some example arrangements the slope can be as low as 5-6degrees slope from the horizontal. In other alternative arrangements ahigher slope of between 5-30 degrees can be used.

FIG. 5 depicts in another cross sectional view 500 a portion of a highvoltage or extra-high voltage capacitor formed utilizing the MESAprocesses, now shown after the MESA oxide etch described above isperformed For continuity, the base numbers of the layers have beenpreserved from the previous figure only incrementing the left digit to“5” including the substrate 510, the prior processing layers 512, theburied capacitor plate 520, the metal barrier 522, the initial Mesaoxide layer 524, the optional etch stop layer 526 and the primary MESATEOS layer 530 showing the sloped edge transition in region 545.

Depicted in FIG. 5 is the sloped transition region 545 now formed in thelayer of primary MESA TEOS material 530. The approximate desired angle548 to enable the subsequent etches and processing to work effectivelycan be from approximately 5 degrees to approximately 30 degrees from thehorizontal plane. (Note that the figures are for illustration andexplanation purposes and are not drawn to scale).

FIG. 6 depicts in another cross section 600 a high voltage or extra-highvoltage capacitor utilizing the MESA formation at a subsequentprocessing step, illustrating the top capacitor plate metal deposition.For continuity, the base numbers of the layers have been preserved fromthe previous figure only incrementing the left digit to “6” includingthe substrate 610, the prior processing layers 612, the bottom capacitorplate 620, the metal barrier 622, the initial MESA oxide layer 624, theetch stop layer 626 and the primary MESA TEOS layer 630 with sloped edgein region 645.

At this stage of the fabrication, in FIG. 6 an optional layer forimproving performance of the MESA capacitor structure 632 is appliedover the primary MESA TEOS layer 630. This layer and the methods forforming the layer is described in a co-owned pending patent application,U.S. patent application Ser. No. 14/277,851, entitled “HIGH BREAKDOWNVOLTAGE MICROELECTRONIC DEVICE ISOLATION STRUCTURE WITH IMPROVEDRELIABILITY,” filed on May 5, 2014, which is hereby incorporated in itsentirety by reference herein. Layer 632 is a dielectric layer that canbe formed from at least a pair of sub-layers, the first sub-layer formedon the MESA capacitor dielectric can be a silicon oxide nitride(oxynitride), and a second sub-layer formed on the capacitor dielectriccan be a silicon nitride layer. As is shown below, dielectric layer 632can be patterned after deposition as described in the above referencedpatent application to form an opening spaced laterally from a top plateconductor, thereby reducing leakage current and also reduces an electricfield at the corners of the top plate conductor. The layer 632 conformsto the upper surface of the MESA dielectric 630 and has the same slopedshape in region 645 as the MESA dielectric layer 630.

After layer 632 is formed, which if it includes both the layersdescribed above can be described as a “bi-layer” dielectric, an etchstep can be performed to create bond pad openings in the dielectriclayers at areas away from the thick MESA dielectric portion of 630, suchas in region 647 in FIG. 6.

A top plate conductor 640 is shown in FIG. 6 is then disposed over theoptional dielectric layer 632 and the bond pad opening in region 647,which portion of the top plate metal numbered 640 b contacts lower plate620. The top plate conductor 640 can be an aluminum cap layer that issputtered on the wafer or substrate, for example. Following theformation of the optional dielectric layer 632, the top level metal 640is applied to the wafer approximately to a thickness between 7000 A to12000 A. The top metal 640 can be, in one example method, sputtered onthe wafer, patterned and then etched to leave the top capacitorcontacts. The top metal is generally comprised of at least two metallayers, a refractory metal barrier layer such as TiN, TiW, or TaN, andthen an aluminum, aluminum-copper alloy, or a copper layer. Because theedge of the MESA 630 was sloped in the prior etch, as shown in region645, and especially for the case of metal removal by RIE anisotropicetch processing, the subsequent etch is able to effectively clear thesloped area of the top level metal, thus not leaving any metal fragmentsthat might otherwise concentrate the electric field within thecapacitor, possibly leading to premature voltage breakdown.

Top level metal 640 can be an aluminum, a copper, or layers of bothaluminum and copper as is known in the art. Top level metal 640 willcomprise at least 2 layers, first of which is a barrier refractory metalsuch as TiN, TiW, TaN, and the overlying metal is typically either asputtered Al alloy such as Al-0.5at % Cu or electroplated Cu. A bond pad(not shown in these figures for simplicity) that is typically of metalincluding copper, gold, nickel and alloys of these, is then formed toprovide a terminal for the top plate 640 of the capacitor. After the topplate metal is formed, it is patterned to separate the top plate portion640 from the bottom plate bond pad portion 640 b. Bond wires or otherconnectors can then be attached to enable connection to the capacitorplates. Alternatives include making connections to other components inthe package or on the integrated circuit. In an arrangement, the topplate is a high voltage terminal and is coupled by a bond pad and ballbond connector to an external circuit, while the bottom plate 620 andbond pad 640 b can be coupled to low voltage circuitry that can be, inone example arrangement, disposed on the same substrate 610 to form anintegrated circuit. In other arrangements, the bottom plate 620 and bondpad 640 b can also be coupled to other circuitry using another ball bondconnection.

FIG. 7 depicts in another cross section 700 a portion of an arrangementincluding a high voltage or extra-high voltage capacitor utilizing theMESA formation at a later processing stage and illustrates the POformation. For continuity, the base numbers of the layers in FIG. 7 havebeen preserved from the previous figure only incrementing the left digitto “7”, including the substrate 710, the prior processing layers 712,the bottom capacitor plate 720, the metal barrier 722, the initial MESAoxide layer 724, the optional etch stop layer 726, the primary MESA TEOSlayer 730, optional dielectric 732, and the top plate metal 740 andbottom plate contact 740 b. The sloped region 745 is in the transitionfrom the thicker MESA portion, to the thinner portion, of the capacitorstructure. An opening in region 749 is shown formed in the optionaldielectric layer 732 by pattern and etch photolithography steps as isdescribed in the above referenced patent application, to increaseperformance. However, in an alternative arrangement, the layer 732 maybe omitted.

At this stage of the fabrication, in FIG. 7 a first layer of aprotective overcoat (PO) 742 usually consisting of silicon dioxide canbe deposited on the wafer to a thickness between approximately 0.8 um toabout 2.2 um thick. Next, without any CMP, a second PO layer 744consisting of silicon oxynitride is applied approximately 0.7 um to 3ums thick. Both of these layers remain as conformal coating layerswithout planarization. This novel approach is important to theprocessing of the arrangements since the MESA structures are still toothick for the use of CMP to level the wafer surface without also cuttinginto the MESA structure. Accordingly, no CMP is used on these PO layers.

FIG. 8 depicts in another cross section 800 a high voltage or extra-highvoltage capacitor arrangement utilizing the MESA formation at asubsequent processing stage and illustrates formation of bond wireopenings in the PO layers deposited in the step of FIG. 7. Forcontinuity, the base numbers of the layers have been preserved from theprevious figure, only incrementing the left digit to “8” including thesubstrate 810, the prior processing layers 812, the bottom capacitorplate 820, the metal barrier 822, the initial MESA oxide layer 824, theoptional etch stop layer 826, the primary MESA TEOS layer 830, thedielectric layer 832, the top plate conductor 840, the 1^(st) PO layer842 and the 2^(nd) PO layer 844. The sloped transition region is shownas element 845. A lower plate bond area is formed by conductor 840 b. POlayers 842, 844 follow the sloped surface of the previous layers inregion 845, and these layers follow the sloped wall of the conductor 840b in region 847. The top plate 840 is exposed in region 843 for forminga bond pad or other terminal contact.

FIG. 9 depicts in another cross section 900 of a high voltage orextra-high voltage capacitor arrangement utilizing the MESA formationsuch as is shown in FIG. 8 at a subsequent processing stage now readyfor PI pattern and etch. For continuity, the base numbers of the layershave been preserved from the previous figure only incrementing the firstdigits to “9” including the substrate 910, the prior processing layers912, the bottom capacitor plate 920, the metal barrier 922, the initialMESA oxide layer 924, the etch stop layer 926, the primary MESA TEOSlayer 930, the optional dielectric layer 932, the top capacitor plate940 and lower plate contact 940 b, the 1^(st) PO layer 942, the 2^(nd)PO layer 944 and a top polyimide or PI layer 950. The sloped transitionregion is shown as element 945.

FIG. 10 depicts in another a cross section 1000 a completed high voltageor extra-high voltage capacitor arrangement utilizing the novel MESAformation processes of the present application. For continuity, the basenumbers of the layers have been preserved from the previous figure onlyincrementing the left digit to “10” including the substrate 1010, theprior processing layers 1012, the bottom capacitor plate 1020, the metalbarrier 1022, the initial MESA oxide layer 1024, the etch stop layer1026, the primary MESA TEOS layer 1030, the optional dielectric layer1032, the top capacitor plate conductor 1040 shown exposed in region1043, the 1^(st) PO layer 1042, the 2^(nd) PO layer 1044 and the top PIlayer 1050, and the bottom plate contact area 1040 b in region 1047. Inan example arrangement, the top metal plate is a bilayer sputtered filmconsisting of TaN and Al0.5% Cu layer. This forms the upper plate of thecapacitor.

In FIG. 10, the capacitor symbol 1055 illustrates where the capacitor isformed with the bottom capacitor plate 1020 serving as the firstterminal and the top capacitor plate 1040 serving as the secondterminal. The MESA structure thickness 1030 is clearly the dominatingdimension for separating the capacitor plates, providing (along withlayer 1032, and the layers 1026 and 1020), a dielectric thickness “d”which in turn predicts the capacitor breakdown voltage as shown inEquation 1.

FIG. 11 depicts in another cross-sectional view an example MESAstructure 1100 for use with the arrangements shown at a processing stageprior to the MESA etch processes described above. In FIG. 11, the layer1120 includes a copper or other metal layer that forms the bottom plateof the capacitor structure and any intervening dielectric layers such asintra-metal dielectric (IMD) or interlevel dielectric layers (ILD) andcan include oxides, nitrides, oxynitrides and high-K and low-Kdielectrics. In this arrangement the MESA capacitor structure can beinserted into a prior semiconductor fabrication process that usesmultiple level metals and inter-metal dielectrics. A silicon nitridebarrier layer 1122 is shown formed on the layer of prior materials 1120and can be, for example, of thickness of about 0.05-0.2 microns.Following the barrier layer 1122, an oxide layer labeled “sub-ESL MESAoxide” 1124 is formed, and this layer can be of thickness from 0.3-1.0ums, for example. An etch stop layer 1126, which is shown as siliconoxynitride or SiON, is then formed over the sub-ESL MESA oxide layer.This layer is used to enable selective etch of the MESA oxide layer tobe deposited. The etch stop layer is relatively thin and can be ofthickness from about 0.1-0.5 ums, for example.

Finally the MESA oxide layer 1130 is formed over the etch stop layer1126. As is described above, in one arrangement this layer can be formedin a single deposition step to provide a monolithic oxide dielectriclayer. However, the thickness needed for high voltage or extra-highvoltage applications is quite large, for example, from about 6 ums toabout 12 ums. This very thick layer of oxide formed over the entirewafer can cause substantial wafer bow or warpage. While the subsequentoxide etch processes will remove most of this layer from areas where itis not needed and thus relieve the wafer bow or warp, the stress on thewafer is significant in this approach. However, to form the thick layer1130 in a single deposition step requires a substantial deposition timein a processing chamber, for example in a TEOS processing chamber, andthe thick oxide is also deposited on the walls of the processingchamber. A plasma etch and clean process is then performed to remove thethick oxide from the walls of the chamber prior to the next wafer beingprocessed. In an alternative approach contemplated by the inventors asforming additional arrangements of the present application, multipledepositions of TEOS oxide, for example, can be performed in a sequenceto reduce the tool cleaning time and multiple chamber tools can be usedso that while a deposition is proceeding in one chamber, another isbeing cleaned and ready for another deposition. Throughput andreliability of the deposition oxide can be increased using theseapproaches. MESA dielectric layer 1130 can be formed using multipledeposition steps, and this approach reduces tool clean time andincreases throughput.

FIG. 12 depicts in another cross sectional view 1200 an alternativearrangement for forming the MESA oxide which reduces the stressexperienced by the wafer. In FIG. 12, the numbers used are repeated fromFIG. 11 for continuity; however the first two digits are incremented to“12”. In FIG. 12, MESA oxide structure 1200 includes the underlyinglayers including a metal bottom plate 1220, a sub-ESL oxide layer 1224,a silicon oxynitride etch stop layer 1226, and the MESA dielectricdeposition layer 1230. In this non-limiting, example arrangement, a MESAoxide deposition of about 8 ums is desired. Of course other thicknessescan be obtained and these variations are contemplated as formingadditional novel arrangements. In this illustrative arrangement, theoxide layers that make up MESA deposition 1230 are formed using a TEOSsource gas in a CVD or PECVD chamber. In this deposition, the process isvaried to provide various thicknesses and stresses in the oxide layers.For example, the sub-ESL oxide layer 1224 is deposited to an examplethickness of 5 k Angstroms (0.5 ums). An etch stop layer 1225 is thendeposited over the initial oxide deposition to a thickness of about 3-4kA. The etch stop layer (ESL) is used in a selective etch to pattern theMESA oxide structure and can be, for example, a silicon nitride, orsilicon oxynitride, layer. In FIG. 12, the example shows a siliconoxynitride (SiON) etch stop layer 1226. The MESA oxide structure 1230 isshown formed using multiple depositions of approximately equalthickness. In an alternative approach that is also contemplated as anadditional arrangement, however, different thicknesses layers could beused. These sub-layers are numbered 1230 a, 1230 b, 1230 c, and 1230 d.In this non-limiting example, a series of oxide depositions of 1.9 ms(19 kA) thickness is made. Further, in forming the oxide 1230 inmultiple steps, in situ cooling can be performed between depositionswhich further reduces stress on the equipment and the wafers. The oxideuniformity in layer 1230 is improved by forming multiple layers 1230a-1230 d of smaller thickness, versus a single layer deposition process.The amount of wafer bow or warp is greatly reduced or can be eliminatedwhen the multiple deposition approach of FIG. 12 is used. Note that thethickness of layer 1230, and of each of the sublayers 1230 a-1230 d, isarbitrary and this illustration presents but one example arrangement ofmany that can be formed using the aspects of the present application.Variations in the thicknesses form additional arrangements that arecontemplated by the inventors and which fall within the scope of theappended claims. The use of the etch stop layer 1226 improves theuniformity of the remaining sub-ESL oxide layer after MESA etch. Thetotal thickness obtained for the MESA structure including the ESL layerand the sub-ESL oxide layer in this non-limiting example is 8.4 ums.This thickness is obtained from the sum of four equal layers of 1.9 ms(7.6 ums) plus an ESL layer 1226 of 0.3 ums and a sub-ESL layer 1224 of0.5 ums. Other dielectric thicknesses can be obtained by addingadditional deposition steps or reducing the number of deposition stepsin forming layer 1230. In addition, the layers can be of varyingthicknesses and of unequal or equal thicknesses.

FIG. 13 depicts in another cross section 1300 an additional alternativearrangement for forming the MESA oxide structure with reduced stress onthe wafer. In FIG. 13 the structure is shown after the MESA dielectricdeposition and prior to etch of the MESA structure. In FIG. 13, MESAoxide structure 1300 includes the underlying layers including a metalbottom plate 1320, a sub-ESL oxide layer 1324, a silicon oxynitride etchstop layer 1326, and the MESA dielectric deposition layer 1330. In FIG.13, the MESA dielectric structure 1330 is formed of alternating oxidelayers 1330 a, 1330 b, 1330 c, 1330 d, 1330 e, 1330 f, 1330 g exhibitingtensile and compressive stress. As is known to those of skill in the artof oxide deposition using TEOS sources, the pressure, temperature,deposition time, and gas concentration can be varied to form eithercompressive, or tensile, oxide layers. Depositing layers using a higherpressure or higher RF power can create a compressive layer; while incontrast, using a lower RF power or lower pressure can create a tensilelayer. In the non-limiting example of FIG. 13, the layers include layersof compressive stress (1330 a, 1330 c, 1330 e, 1330 g) that are 19 kA(1.9 ms) thick alternating with layers of tensile stress (1330 b, 1330d, 1330 f) that are 11 kA (1.1 ums) thick. Variations in processingparameters can be used to create additional or fewer layers, and layersof compressive, neutral, or tensile stress and these variations createMESA structures that form additional arrangements contemplated by theinventors of the present application and which also fall within thescope of the appended claims. By alternating the layers to formcompressive stress and tensile stress oxide layers one upon another, thestress on the wafer, and the resulting wafer bow or warp, is reduced oreliminated completely. In this approach the wafer stress and wafer boweffects that would occur in a single deposition of the MESA oxide asdescribed above is removed. The example MESA oxide 1330 of FIG. 13includes a total thickness above the bottom metal plate 1320 of 11.4ums, that thickness includes 4 layers of compressive stress oxide (1330a, 1330 c, 1330 e, 1330 g) at 1.9 ms (7.6 ums total), 3 layers oftensile stress material (1330 b, 1330 d, 1330 f) at 1.1 ums each, (3.3ums total), and a layer 1324 of ESL material, in this example, 0.3 ums,and a layer of sub-ESL oxide, in this example, 0.5 ums. When addedtogether the thickness of the resultant dielectric structure shown in1300 is 11.7 ums. The dielectric thickness can be increased by usingmore layers or reduced by using fewer layers.

FIG. 14 depicts in another cross sectional view 1400 an example highvoltage or extra high voltage capacitor arrangement formed using theMESA structures and processes of the present application. Forcontinuity, the base numbers of the layers have been preserved from theprevious figures only incrementing the left digit to “14” including thesubstrate 1410, the bottom capacitor plate 1420, the primary MESA TEOSlayer 1430, the two layer dielectric 1432, the top metal plate 1440, the2nd PO layer 1444 and the top PI layer 1450.

In FIG. 14, a high voltage capacitor area 1455 labeled “HV Cap Area” isshown and a high voltage capacitor ground ring area 1457 labeled “HV Capground ring area” is shown in an adjacent portion of the structure. Theslope region 1445 makes the transition from the HV Cap Area 1455 to theHV Cap ground ring area 1457.

In FIG. 14, a silicon or other semiconductor material forms substrate1410. A bottom plate 1420 is formed over the initial metal and intrametal dielectric layers. For example bottom plate 1420 can be formedalong with metal layer two. After metal layer three and intra-metallayers are formed, and after an etch stop layer is deposited, MESAcapacitor dielectric layer 1430 is formed using any of the depositionmethods described above, such as forming multiple depositions in asequence in a single processing tool or in multiple chambers of one ormore processing tools.

The silicon oxide-silicon oxynitride dielectric layer 1432 in FIG. 14 isformed over the MESA capacitor dielectric layer 1430 and has an opening1449 spaced from the edge of top plate conductor 1440. The sloped region1445 is shown transitioning from the high voltage capacitor area 1455 tothe lower voltage capacitor area 1457 at an angle from the horizontal.PO layers 1444 and 1455 are shown overlying the structure.

In FIG. 14, several structures are shown that can be used to shield orprovide additional ground rings for the high voltage capacitor. AFaraday cage 1465 is shown formed approximately 40 ums from the edge ofthe top plate 1440 in the high voltage capacitor region and this Faradaycage is coupled to the substrate 1410 and including a metal-1 portionand a metal-2 stacked portion that is electrically connected together.This optional Faraday cage can surround the capacitor as a ring andprovide additional shielding. A third level metal (MET3) portion 1467 isused as a ground ring and is formed at about 70 ums horizontal spacingfrom the high voltage capacitor. A damascene copper metal portion 1469labeled METDCU is formed between nitride barrier layers and extendingthrough an intra-metal dielectric or IMD oxide and is positioned 100 umshorizontal spacing from the high voltage capacitor. A ground ringstructure 1471 is formed from the top metal at the right side of thestructure. Each of these shielding structures can be used independentlyor in combination with the high voltage or extra high voltage capacitorstructure to increase the performance and reduce noise effects andunwanted coupling. The spacing distances shown are examples and can bemodified using known simulation tools to suit a particular applicationor semiconductor process. The thickness of the dielectric, here shown as15.1 ums, can also be modified as described above and any one of theapproaches to forming the dielectric layer 1430 can be used, either asingle deposition, multiple oxide depositions, or tensile andcompressive stress oxide layers in alternating depositions, can be usedwith the ground rings and shields to increase performance.

FIG. 15 depicts in another cross sectional view 1500 an alternativearrangement for a MESA capacitor structure that forms an additionalaspect of the present application. Numbers for elements that are similarto those shown in the figures above are again used but with the firsttwo digits now replaced with “15”. Substrate 1510 can be silicon, oranother semiconductor material such as gallium arsenide, or an epitaxiallayer of semiconductor material, and may have various components such asMOS transistors, diodes, FETs, bipolar transistors, resistors andcapacitors formed within it. FIG. 15 illustrates an arrangement wherethe MESA structure and formation method are used with a two level metalsystem in a semiconductor process. The bottom plate of a high voltage orextra high voltage capacitor is formed using the metal one layer, whichcan be a metal conductor such as copper, aluminum, and alloys thereof,for example. A MESA oxide dielectric layer 1530 is then formed over themetal one layer. A diffusion barrier (not shown for simplicity in FIG.15) can be deposited over the metal and lie between the metal and theMESA oxide layer. The MESA oxide layer 1530 can be formed as a singledeposition oxide layer, or using the multiple oxide depositions or usingthe compressive/tensile stress oxide layers as described above. The MESAoxide layer 1530 is shown in FIG. 15 after etch to create the slopedtransition area 1545. After the sloped transition in area 1545 iscreated by MESA etching regions where a graded photoresist technique wasemployed, a second level oxide layer 1535 is deposited. This oxide layer1535, labeled OXIDE 2, is the same oxide layer that would be usedbetween metal-1 and metal-2 in the two level metallization system. Theoxide layer 1535 lies conformally over the MESA oxide 1530 and followsthe sloped region in transition area 1545.

Following the deposition of the oxide 1535, which can also be a nitride,oxynitride, or other dielectric layer, the metal-2 layer is depositedover the wafer. In FIG. 15 the metal-2 layer portion 1532 is shownforming the top capacitor plate, and is illustrated after pattern andetch steps have been used to form the top plate.

A protective overcoat layer 1536 is then formed and an opening labeledPOR2 is patterned and etched to expose the top surface of 1532.Connections can then be made for the top plate such as a wire bond andwire ball 1555 as illustrated in FIG. 15. In another portion of thesubstrate 1510, a second protective overcoat opening labeled POR1exposes a portion of the metal-1 layer 1520 to allow a connection suchas 1565 to be made to the bottom plate of the capacitor. A scribe line1575 labeled “Closed Scribe” is form adjacent the connection 1565.

In an example semiconductor process, the thickness of the dielectriclayer for the high voltage capacitor which is the sum of the thicknessesof the MESA oxide 1530 and the Oxide 2 layer 1535 that are positionedbetween the top of the bottom plate 1520 and the bottom of the top plate1532 is 19 ms. This is but one non-limiting illustrative example andmany other dielectric thicknesses can be obtained using the novel MESAstructures and methods of the present application in a two levelmetallization system.

FIG. 16 depicts in a top view 1600 a portion of a high voltage or extrahigh voltage capacitor arrangement formed using the novel MESA structureand methods of the present application. In FIG. 16 the top plateportions 1632 are shown with metal two exposed. The high voltage region1655 is the top of the protective overcoat over the MESA structure. Thetransition sloped region 1645 lies outside the high voltage region, andthe low voltage region 1657 lies outside the sloped region 1645 andprovides the ground ring or low voltage areas as described above.

FIG. 17 depicts in a flow diagram an example method arrangement 1700 forforming the MESA structures and high voltage or extra high voltagecapacitors. In FIG. 17, fifteen steps are arranged with the primary flowhaving eight sequential steps (1710, 1712, 1714, 1720, 1724, 1726, 1730and 1732) with an optional step 1716 after 1714 and alternate steps1722, 1723 that parallel 1720. Consequence indicators 1750, 1751 and1752 surround step 1724.

The starting point 1710 of method 1700 is a wafer processed normally ina semiconductor fabrication process. In processing the wafer, variousintegrated circuit devices including transistors, passive components,interconnections and the like are used to form circuitry on a pluralityof integrated circuits. Power circuitry such as power supplies,converters, transformers and the like can be implemented on theintegrated circuits on the wafer. In addition, various digital circuitrysuch as controllers and processors can be implemented and can beintegrated with the other functions to provide highly integratedcircuitry.

The highest metal layer formed in the semiconductor process prior to thestart of method 1700 becomes the first or bottom capacitor plate in aparallel plate capacitor. The next steps of method 1700 provide abarrier to prevent metal migration in step 1712 and a base layer ofsilicon dioxide in step 1714. At this point, an optional etch stop layer1716 may be provided to the wafer to assist in the later etching of theMESA layer. After the optional etch stop layer is formed in 1716, eithera single layer (step 1720) or multiple layers of TEOS (silicon oxide)(step 1722) or alternating layers of compressive and tensile stresslayers (step 1723) are provided to create the MESA dielectric. Theconsequence indicator 1750 shows that wafer warpage is likely to occurat this point if a thick MESA layer is formed in a single layer. Theconsequence indicator 1751 illustrates that the wafer warpage is minimalif the alternating stress and tensile layers of step 1723 are used toperform the MESA structure.

The next step, 1724, is to etch the MESA TEOS layer to relieve thestress. In that etch operation, a sloped edge is etched into the thickMESA layer which forms a boundary between the thickest region of theMESA dielectric, protected by photoresist during etch, and the low-levelregions which had no photoresist protection during the etch. After etch,consequence indicator 1752 shows that wafer warpage (to the extent thatany is present) is relieved. Following the etch is step 1724, there aretwo remaining steps, the first is to provide a high voltage enhancementlayer in step 1726, or in an alternative method, to skip forming thishigh voltage enhancement layer in step 1727; and the second is toprovide top level metal in step 1730 which becomes the second or topplate of the capacitor. In the final state 1732, the wafer processingcontinues to complete the wafer fabrication. Following the formation ofthe MESA structure, the remaining processing avoids CMP steps to preventdamaging the thick MESA structure.

FIG. 18 depicts in a block diagram an example application for isolationusing a capacitor of the arrangements in a circuit 1800. In FIG. 18, atransmitting amplifier 1801 is shown coupled to one plate of anisolation capacitor 1803. A receiver amplifier 1805 is shown coupled tothe opposite plate of the isolation capacitor 1803. The two amplifiers1801 and 1805 are remote from one another and on different groundpotentials such that a ground potential difference, shown as voltageVgpd, exists. By using an isolation capacitor, the two grounds are nottied together but remain isolated from one another. There is no DC pathbetween the two amplifiers and signals from the transmitter 1801 can bereceived at the receiver 1805 reliably as a result.

FIG. 19 depicts in a circuit diagram an application for isolationcapacitors using the arrangements of the present application. In FIG.19, a transmitter circuit 1901 that is in a first power domain is showntransmitting signals to a receiver circuit 1921. In FIG. 19, thetransmitter has both low-frequency and high frequency channels. The lowfrequency channel is sampled using an oscillator 1903 to provide a clockto a pulse width modulation function 1905. The data samples are outputto an inverting amplifier A1 and a non-inverting amplifier A3 to providea differential signal as an output. In a parallel path, high frequencysignals are input to an inverting amplifier A5 and a non-invertingamplifier A7 to provide a second differential output signal. Thereceiver circuit 1921 has a separate power and ground domain so thatthere would be a differential voltage between ground potentials, forexample. At the inputs of receiver circuit 1921, capacitors C1, C3, C5and C7 are coupled to isolate the input signals from the remainder ofthe circuit 1921 and to provide an isolation barrier. Offset voltagesare compensated using a reference voltage Vref and resistors R1, R3, andR5, R7. The input signals from the capacitors C1, C3, C5, C7 are theninput to pairs of Schmitt trigger amplifiers with hysteresis to provideglitch prevention noise reduction, and then latched by logic gate 1925,1927 (low frequency signals) and gates 1931, 1933 (high frequencysignals). The outputs of the low frequency path are low pass filtered atLPF 1937, and input to an output multiplexer 1939. The outputs of thehigh frequency path are input to a decision block DCL 1935 and to theother input of the output multiplexer 1939. The receiver circuit canoutput either high frequency or low frequency signals at the OUTterminal. The high voltage or extra-high voltage capacitors of thearrangements are used to provide the isolation capacitors C1, C3, C5 andC7 so that the two circuits are galvanically isolated. The receiver 1921and the transmitter 1901 can be separate circuits, separate circuitboards, separate integrated circuits or remote portions of a circuitboard or integrated circuit. The capacitors C1, C3, C5, and C7 can beintegrated with the remaining components in receiver 1921 for example,or provided as discrete components or as a module or analog integratedcircuit.

FIG. 20 depicts in a block diagram an example arrangement 2000 thatincorporates the isolation capacitors of the present application. InFIG. 20, a transmitter circuit 2001 is coupled to a receiver circuit2005. As shown in FIG. 20, the two circuits can be individual integratedcircuit dies. In a non-limiting example arrangement, the two integratedcircuits can be coupled by bond wires, balls such as BGA balls, bumps,solder columns, or the like. In one non-limiting example the twointegrated circuits 2001, 2005 can be IC dies disposed in a singlepackage. In additional alternative arrangements, the two integratedcircuits 2001, 2005 can be provided in separate packages.

In the example arrangement depicted in FIG. 20, the transmitter 2001 isshown with wire bond connections coupling the amplifiers A1, A5, whichare differential signal amplifiers in this non-limiting example, to thetop plates of the capacitors C1, C3, C5, and C7 that are disposed on thereceiver 2005. The example in FIG. 20 shows wire connections, e.g. bondwires, between the two devices, however other connections such as solderballs, solder columns, solder bumps, micro-BGA or BGA balls and thelike, can be used to connect the two devices.

Because the transmit IC 2001 is coupled to the top plate of thecapacitors on the receiver device 2005, and the capacitors are the highvoltage or extra high voltage capacitors of the arrangements asdescribed above, the two circuits are galvanically isolated one fromanother. The receiver amplifiers S1, S5 are coupled to the low voltageportions of the capacitors C1, C3, C5, C7, that is, by coupling to thebottom plates. The receiver circuit shows differential inputs to a firstamplifier S1 and a second amplifier S2, one for the low frequencychannel, for example, and one for the high frequency channel, and aselector 2007 selects the channel for transmitting as an output.

Various modifications can also be made in the order of steps and in thenumber of steps to form additional novel arrangements that incorporateaspects of the present application, and these modifications will formadditional alternative arrangements that are contemplated by theinventors as part of the present application and which fall within thescope of the appended claims.

Although the example illustrative arrangements have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the present application as defined by the appended claims.

Moreover, the scope of the present application is not intended to belimited to the particular illustrative example arrangement of theprocess, machine, manufacture, and composition of matter means, methodsand steps described in this specification. As one of ordinary skill inthe art will readily appreciate from the disclosure, processes,machines, manufacture, compositions of matter, means, methods or steps,presently existing or later to be developed, that perform substantiallythe same function or achieve substantially the same result as thecorresponding example arrangements described herein may be utilizedaccording to the illustrative arrangements presented and alternativearrangements described, suggested or disclosed. Accordingly, theappended claims are intended to include within their scope suchprocesses, machines, manufacture, compositions of matter, means,methods, or steps.

What is claimed is:
 1. A method, comprising: providing a semiconductorsubstrate; forming a capacitor bottom plate of conductive materialoverlying the semiconductor substrate; forming a capacitor dielectriclayer overlying at least a portion of the capacitor bottom plate, thecapacitor dielectric layer having a thickness of at least 6 ums; forminga gradient photoresist layer over the capacitor dielectric layerdefining a first region in the capacitor dielectric having a firstthickness and a defining a second region having a second thickness thatis less than the first thickness; etching the capacitor dielectric layerto form the first region, the second region, and forming a transitionregion between the first region and the second region, the transitionregion having a sloped top surface with a slope from a horizontal planegreater than about 5 degrees; and forming a top plate conductoroverlying at least a portion of the first region of the capacitordielectric layer.
 2. The method of claim 1, wherein forming thecapacitor dielectric layer comprises forming in a single deposition stepa monolithic capacitor dielectric layer that is one selected from thegroup consisting essentially of an oxide layer and an oxynitride layer.3. The method of claim 2, wherein forming in a single deposition stepfurther comprises performing a TEOS deposition.
 4. The method of claim1, wherein forming the capacitor dielectric layer further comprisesforming the capacitor dielectric layer in a series of dielectricdeposition steps to form multiple layers of dielectric.
 5. The method ofclaim 4 wherein forming the multiple layers of dielectric comprisesforming a series of layers each one selected from the group consistingessentially of an oxide layer and an oxynitride layer.
 6. The method ofclaim 1, wherein forming the capacitor dielectric layer furthercomprises a series of dielectric deposition steps to form alternatingcompressive layers and tensile layers of dielectric.
 7. The method ofclaim 1, and further comprising forming at least one insulating layerbetween the bottom plate and the capacitor dielectric layer, theinsulating layer having a thickness of at least 3 ums.
 8. The method ofclaim 7 wherein a sum of the thicknesses of the capacitor dielectriclayer and the thickness of the at least one insulating layer is greaterthan about 9 ms.
 9. The method of claim 8, wherein an area of thecapacitor dielectric layer is less than 25% of a total area of thesemiconductor substrate.
 10. The method of claim 1, and furthercomprising forming an upper layer over the capacitor dielectric layerthat lies between the top of the capacitor dielectric layer and the topplate conductor, the upper layer comprising silicon nitride and siliconoxynitride.
 11. The method of claim 10, and further comprising formingopenings in the upper layer by photolithographic pattern and etchprocesses.